91L near tropical depression status

By: Dr. Jeff Masters , 2:08 PM GMT on August 02, 2010

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A tropical wave near 12N 41W, midway between Africa and the Lesser Antilles Islands, is very close to being a tropical depression. NHC labeled this system Invest 91L yesterday, and is giving it a 90% chance of developing into a tropical depression by 8am Wednesday. Wind shear is a low 5 - 10 knots, sea surface temperatures are at record highs, and the dust and dry air of the Saharan Air Layer (SAL) are far enough to the north of 91L to potentially allow further development. The main negative for development appears to be the storm's small size, which makes it vulnerable to modest increases in wind shear or dry air entrainment. A Windsat pass from 5am EDT this morning did not show a closed circulation. Satellite imagery shows that the intensity and areal extent of 91L's heavy thunderstorms is very limited, but that a closed surface circulation may be close to forming. Low-level spiral bands and upper-level outflow are not apparent yet.


Figure 1. Morning satellite image of Invest 91L.

Forecast for 91L
There is modest model support for 91L developing into a tropical depression. Three out of six of our reliable models for forecasting tropical cyclone genesis predict 91L will develop into a tropical depression by Tuesday or Wednesday. A west-northwest motion at 10 -15 mph is predicted, which should carry 91L a few hundred miles northeast of the northernmost Lesser Antilles Islands. However, it is possible that 91L would track over the northernmost Lesser Antilles Islands, as predicted by the Canadian model. Squalls from the outer rainbands of 91L may affect islands such as Antigua and Barbuda as early as Wednesday afternoon. As 91L makes its closest approach to the Lesser Antilles on Wednesday, the storm will begin to encounter strong upper-level westerly winds associated with the counter-clockwise flow of air around an upper-level low pressure system centered between Bermuda and Puerto Rico. The latest SHIPS model forecast predicts that these winds will cause wind shear to rise to the moderate level, 10 - 20 knots, by Tuesday night, and to the high level, 20 - 30 knots, by Wednesday. There is also a great deal of dry air associated with the upper level low that may cause problems for 91L. The high wind shear and dry air should weaken and possibly destroy 91L late this week.

A trough of low pressure is expected to move off the U.S. East Coast on Friday, and this trough may be strong enough to recurve 91L far enough to the northwest that the storm will threaten Bermuda. The HWRF and ECMWF models predict 91L could pass very near to Bermuda on Saturday. It is uncertain at this time if the trough will be strong enough to recurve 91L all the way out to sea early next week, as predicted by the GFS model, or leave 91L behind to potentially move westward again into the U.S. East Coast, as predicted by the Canadian model. The amount of wind shear that might be present early next week is also highly uncertain.

Cyprus records its hottest temperature in history yesterday
The island of Cyprus recorded its hottest temperature in its history on August 1, 2010 when the mercury hit 46.6°C (115.9°F) at Lefconica. The old record for Cyprus was 44.4°C (111.9°F) at Lefkosia in August 1956. An older record of 46.6°C from July 1888 was reported from Nicosia, but is of questionable reliability.

The year 2010 is now tied with 2007 as the year with the most national extreme heat records--fifteen. There has been one country that has recorded its coldest temperature on record in 2010; see my post last week for a list of the 2010 records. My source for extreme weather records is the excellent book Extreme Weather by Chris Burt. His new updates (not yet published) remove a number of old disputed records. Keep in mind that the matter of determining extreme records is very difficult, and it is often a judgment call as to whether an old record is reliable or not. For example, one of 2007's fifteen extreme hottest temperature records is for the U.S.--the 129°F recorded at Death Valley that year. Most weather record books list 1913 as the year the hottest temperature in the U.S. occurred, when Greenland Ranch in Death Valley hit 134°F. However, as explained in a recent Weatherwise article, that record is questionable, since it occurred during a sandstorm when hot sand may have wedged against the thermometer, artificially inflating the temperature. Mr. Burt's list of 225 countries with extreme heat records includes islands that are not independent countries, such as Puerto Rico and Greenland. Seventy four extreme hottest temperature records have been set in the past ten years (33% of all countries.) For comparison, 14 countries set extreme coldest temperature records over the past ten years (6% of all countries). I thank Mr. Burt and weather record researchers Maximiliano Herrera and Howard Rainford for their assistance identifying this year's new extreme temperature records.

Next update
I'll have an update later today if 91L develops into a TD.

Jeff Masters

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Quoting largeeyes:
NHC has it splittin the uprights. Guess we here in NC will keep an eye on him.


And in VA.
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The NHC's track is WAY to far north in my opinion. The models don't have a very good handle on the system yet so I expect that track to shift quite significantly to the left. I'll have an blog update w/my graphics around 5PM today when the system should be a moderate tropical storm in my opinion and the models have a change of heart once they grip on. I'll be back in a few.
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So, is GOM out of the questions at this point??
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11:00 am National Hurricane Center Advisory
**TROPICAL DEPRESSION TWO** Graphics Update
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I'm going with climatology on the track and favor a more southern track. I think the NHC is too far out to sea.
Member Since: September 30, 2005 Posts: 0 Comments: 1606
Quoting AstroHurricane001:


I suspect the Gulf Stream fluctuations and previous volcanic ash may have played a role.



Warm anomalies all around. (Kuroshio anomalies invading the PDO, !!!)


First, perhaps. 2nd hasn't been an issue as far as I'm aware.

Much more driven by B/A High positioning, NAO, and jet stream fluctuation.

While it hasn't been warm, it has been unseasonably dry this year until this month.
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Quoting cirrocumulus:


Looks like outflow is developing and potential spiral banding. It will be very hard for New England to get a tropical cyclone to make landfall here.
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LeeLee, re: your post #83. I got the same message this morning for the first time.
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Did they just add this google map's thing with the interactive cone? This is pretty cool.
Member Since: August 22, 2006 Posts: 0 Comments: 1449
Quoting catastropheadjuster:
Well it's been a horrible Monday so far, we came to our boat shop this morning and someone stole a tower off of one of the boats it cost about 8500.00. This is not good at all. Why are people thieves? Had to vent I could just scream right know, they better hope I don't see it anywhere.
I see we have a wave out there, I see some say it's a fish.
Sheri



someone stole my husband's brand new drill right out of our storage shed connected to the garage. i swear, it ruined the weekend. he could not get over it.
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11:00 am National Hurricane Center Advisory
**TROPICAL DEPRESSION TWO** Graphics Update
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Quoting Neapolitan:


Such a Karen-like track...but it could still impact New England.
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Member Since: September 30, 2005 Posts: 0 Comments: 1606
NHC has it splittin the uprights. Guess we here in NC will keep an eye on him.
Member Since: August 22, 2006 Posts: 0 Comments: 1449
Well it's been a horrible Monday so far, we came to our boat shop this morning and someone stole a tower off of one of the boats it cost about 8500.00. This is not good at all. Why are people thieves? Had to vent I could just scream right know, they better hope I don't see it anywhere.
I see we have a wave out there, I see some say it's a fish.
Sheri

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I am not so sure on the whole fish ideal already. Remember models tend to trend further west over time.
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Member Since: November 8, 2009 Posts: 4 Comments: 13275
Now that it's a depression, everyone can gripe about TD4 not being a tropical storm.
I'd better get to work.
Thanks for all the great info!
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Dang!! I was wrong. I think the NHC is being very conservative on this one. Oh well its their gig not mine..lol..
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Quoting sammywammybamy:


I Dont Believe that it would be strong enough to feel the pull to the north.


that's what i'm worried about. but this blog said bermuda or east coast. is dr. m writing off GOM possibility all together?
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Quoting pub123:
Weather (temp records) isn't climate - simply natural oscillation.


Not entirely true; if average global temperatures were steadily increase over a period of several decades, that'd be a pretty sire sign of climate change...and that's just what we've got.

Quoting pub123:
...unfortunately the records we have compiled so far will need at least 1,000 or 2,000 more years of compilation to be of any practical use in theorizing climate activity.


Not true at all. That's like saying that a man needs to gain 100 pounds in a year before deciding to diet, when disaster could've been prevented had he paid attention to the 4.5 ounces he was putting on each and every day. Waiting 1,000 years is far too long. So is waiting 100, or 10, or even one. In fact, we've waited too long already: the gloabl is heating--rapidly--and we humans are too blame.
Member Since: November 8, 2009 Posts: 4 Comments: 13275
Quoting Cotillion:


Yes, a lot of what I said was tongue-in-cheek, except the last sentence.

Continental Europe has been very hot, but not here. It's been a below average July on the whole. June was alright, though.


I suspect the Gulf Stream fluctuations and previous volcanic ash may have played a role.



Warm anomalies all around. (Kuroshio anomalies invading the PDO, !!!)
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Levi I cant wait for your youtube update
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Im going to take a guess that 91L is currently a TS with winds of 45 on the 11am update.

Lets see what happens.
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000
WTNT24 KNHC 021433
TCMAT4
TROPICAL DEPRESSION FOUR FORECAST/ADVISORY NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042010
1500 UTC MON AUG 02 2010

THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

TROPICAL DEPRESSION CENTER LOCATED NEAR 12.6N 41.1W AT 02/1500Z
POSITION ACCURATE WITHIN 30 NM

PRESENT MOVEMENT TOWARD THE WEST-NORTHWEST OR 290 DEGREES AT 15 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 1006 MB
MAX SUSTAINED WINDS 30 KT WITH GUSTS TO 40 KT.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

REPEAT...CENTER LOCATED NEAR 12.6N 41.1W AT 02/1500Z
AT 02/1200Z CENTER WAS LOCATED NEAR 12.3N 40.3W

FORECAST VALID 03/0000Z 13.5N 44.0W
MAX WIND 35 KT...GUSTS 45 KT.
34 KT... 30NE 0SE 0SW 30NW.

FORECAST VALID 03/1200Z 14.8N 48.9W
MAX WIND 40 KT...GUSTS 50 KT.
34 KT... 30NE 0SE 0SW 30NW.

FORECAST VALID 04/0000Z 16.4N 53.4W
MAX WIND 45 KT...GUSTS 55 KT.
34 KT... 60NE 30SE 0SW 45NW.

FORECAST VALID 04/1200Z 18.4N 57.4W
MAX WIND 50 KT...GUSTS 60 KT.
50 KT... 15NE 0SE 0SW 0NW.
34 KT... 75NE 45SE 30SW 60NW.

FORECAST VALID 05/1200Z 22.0N 63.0W
MAX WIND 50 KT...GUSTS 60 KT.
50 KT... 30NE 0SE 0SW 15NW.
34 KT... 75NE 45SE 30SW 60NW.

EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 200 NM
ON DAY 4 AND 250 NM ON DAY 5...AND FOR INTENSITY NEAR 20 KT EACH DAY

OUTLOOK VALID 06/1200Z 26.0N 66.5W
MAX WIND 45 KT...GUSTS 55 KT.

OUTLOOK VALID 07/1200Z 29.0N 68.5W
MAX WIND 45 KT...GUSTS 55 KT.

REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 12.6N 41.1W

NEXT ADVISORY AT 02/2100Z

$$
FORECASTER BRENNAN

Member Since: July 15, 2006 Posts: 165 Comments: 52262
I keep getting a message that this site has a threat, started showing up yesterday and I've been a daily lurker for 5 years and this is the first time I'm getting such a notice, Norton directs me to this:
Threat Name: Adware.ADH
Location: http://www.wunderground.com/windowsinstall/install_whas11.exe

please don't click on the link, I have no idea what it will do to your computer, but could ADmin, please look into this?

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TCMAT4
TROPICAL DEPRESSION FOUR FORECAST/ADVISORY NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042010
1500 UTC MON AUG 02 2010

THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

TROPICAL DEPRESSION CENTER LOCATED NEAR 12.6N 41.1W AT 02/1500Z
POSITION ACCURATE WITHIN 30 NM

PRESENT MOVEMENT TOWARD THE WEST-NORTHWEST OR 290 DEGREES AT 15 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 1006 MB
MAX SUSTAINED WINDS 30 KT WITH GUSTS TO 40 KT.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

REPEAT...CENTER LOCATED NEAR 12.6N 41.1W AT 02/1500Z
AT 02/1200Z CENTER WAS LOCATED NEAR 12.3N 40.3W



http://www.nhc.noaa.gov/text/refresh/MIATCMAT4 shtml/021433.shtml
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TROPICAL DEPRESSION FOUR FORECAST/ADVISORY NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042010
1500 UTC MON AUG 02 2010

THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

TROPICAL DEPRESSION CENTER LOCATED NEAR 12.6N 41.1W AT 02/1500Z
POSITION ACCURATE WITHIN 30 NM

PRESENT MOVEMENT TOWARD THE WEST-NORTHWEST OR 290 DEGREES AT 15 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 1006 MB
MAX SUSTAINED WINDS 30 KT WITH GUSTS TO 40 KT.
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Quoting AstroHurricane001:


Link - I know, the article still needs a major cleanup.


Yes, a lot of what I said was tongue-in-cheek, except the last sentence.

Continental Europe has been very hot, but not here. It's been a below average July on the whole. June was alright, though.
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I hope Avila writes the first discussion. I suspect he'll be very sarcastic toward Euro's failure to develop what is now TD 4.
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From NWS PR:

A SECOND TROPICAL CYCLONE IS FORECAST TO DEVELOP FROM
ANOTHER TROPICAL WAVE YET TO MOVE OUT OF AFRICA AND PASS FARTHER
NORTHEAST OF THE AREA...BUT THIS IS STILL TOO FAR IN THE FUTURE
FOR ANY CONFIDENCE.
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The intensity models don't really strengthen 04L much more than a moderate-strong TS at best.
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Quoting pub123:
Weather (temp records) isn't climate - simply natural oscillation.

It's encouraging to see records being kept but unfortunately the records we have compiled so far will need at least 1,000 or 2,000 more years of compilation to be of any practical use in theorizing climate activity.


LOL! Sorry, but by then we'll be too roast to take records. But yes, as time moves on the chances of old records, hot or cold being broken increases.
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73. PR51
Quoting oracle28:
Fish storm, err Fish Depression.

That will be its real future...Colin Fish....LOL
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WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1030 AM EDT MON 02 AUGUST 2010
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 03/1100Z TO 04/1100Z AUGUST 2010
TCPOD NUMBER.....10-064

I. ATLANTIC REQUIREMENTS
1. TROPICAL DEPRRESSION FOUR
FLIGHT ONE -- TEAL 70
A. 04/1200,1800Z
B. AFXXX 0104A CYCLONE
C. 04/1000Z
D. 18.4N 57.4W
E. 04/1130Z TO 04/1800Z
F. SFC TO 15,000 FT

2. SUCCEEDING DAY OUTLOOK: FIXES AT 05/0000Z
AND 05/0600Z. BEGIN 12-HRLY FIXES AT 05/1800Z.
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ALERT ATCF MIL 91X XXX 100802000000
2010080200
9.8 323.6
10.5 317.6
100
9.8 323.7
012300
1008012300
1
WTNT21 KNGU 012300
SUBJ/TROPICAL CYCLONE FORMATION ALERT 012300Z AUG 10//
RMKS/1. FORMATION OF A TROPICAL CYCLONE IS POSSIBLE WITHIN 100NM
EITHER SIDE OF A LINE FROM 9.8N 36.3W TO 10.5N 42.3W OVER THE
NEXT 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF A NUMBERED
TROPICAL CYCLONE WARNING AT THIS TIME.
2. A TROPICAL WAVE 950 MILES SOUTHWEST OF THE CAPE VERDE ISLANDS
ALONG 36W SOUTH OF 15N AT 1800Z IS EMBEDDED WITHIN THE ITCZ AND
CONTINUES TO TRACK WEST-NORTHWEST AT 10 TO 15 KNOTS INTO AN AREA OF DECREASED
WIND SHEAR. THE SAHARAN AIR LAYER LOCATED NORTH OF THE SYSTEM HAS
SIGNIFICANTLY DECREASED IN STRENGTH OVER THE PAST FEW HOURS PRODUCING
FAVORABLE CONDITIONS FOR SLOW DEVELOPMENT OF THIS SYSTEM IN THE NEXT 24HRS.
THIS IN CONJUCTION WITH WARM SEA SURFACE TEMPERATURES OF 83 TO 86
DEGREES FAHRENHEIT, ARE HELPING TO ENHANCE THE DEVELOPMENT OF THIS
TROPICAL FEATURE.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO A WARNING OR ALLOWED TO
EXPIRE BY 022300ZAUG 2010.//
9110073106 88N 329W 20
9110073112 89N 335W 20
9110073118 90N 341W 20
9110080100 92N 347W 20
9110080106 94N 353W 20
9110080112 96N 358W 25
9110080118 98N 366W 25
9110080200 101N 374W 25

Member Since: July 15, 2006 Posts: 165 Comments: 52262
I dont know if any of you have seen this, it is weather related I guess, but its the youtube video Jimmy Kimmel had on where the guy sees a douhble rainbow and flips out about it. I dont know what there is about it that is so funny but i cant watch it without dying laughing and its had over 8 million views in just a week. anyway, here it is, i couldnt get it to embed.

Link
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Wow.... I had 3 enteries eaten by the Blog munchers.. or something....

Who has determined this is a TD? and a link if you have one please
Member Since: July 1, 2005 Posts: 10 Comments: 1681
its about time nhc!!!!,probably closer to a TS strength now,should have been a td since 11pm last nigth imo
Member Since: October 5, 2007 Posts: 20 Comments: 4970
I wonder what the first discussion on TD#4 will say considering one of the most reliable models the Euro does not develop it.
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Weather (temp records) isn't climate - simply natural oscillation.

It's encouraging to see records being kept but unfortunately the records we have compiled so far will need at least 1,000 or 2,000 more years of compilation to be of any practical use in theorizing climate activity.
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Quoting oracle28:
Fish storm, err Fish Depression.


Please do not count your oracles before they hatch.
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FNMOC Satellite Data Tropical Cyclone Page

2010 Storms
All Active Year


Atlantic
04L.FOUR

East Pacific

Central Pacific
92C.INVEST

West Pacific
96W.INVEST

Indian Ocean

Southern Hemisphere

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Quoting FloridaHeat:
now that this is a td does that mean the nhc will offer an official track


And we may start getting meaningful model runs. Tomorrow.
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Quoting Cotillion:
Heatwaves? In Europe?

Cannot be.

We wait in anticipation to break 70 at the end of the week.


Link - I know, the article still needs a major cleanup.
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Fish storm, err Fish Depression.
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.